Three basic areas of investigation will be pursued in the proposed research project. A) Human studies: study of the structural organization of layer 1 of the cerebral cortex during the course of embryonic development (cortical ontogenesis). The rapid Golgi method -a specialized silver neurohistological technique - will be used in this study. B) Experimental studies: 1) Study of the growth of blood vessels in the cerebral cortex during the course of early embryonic development. The cerebral cortices of young embryos from the cat, the hamster and the mouse will be investigated and the rapid Golgi method will be used. 2) Golgi study of the embryonic olfactory mucosa of hamster and mouse embryos. This study will analyze the development of the intrinsic olfactory neurons and will try to determine the possible presence of intrinsic or extrinsic innovation of the olfactory mucosa. C) Anatomic-pathologic studies: investigation of the cause, distribution, incidence and demise of prematures born at the Medical Center of our Institute or those referred to it from surrounding communities. Social, clinical and pathological data will be utilized in this study. BIBLIOGRAPHIC REFERENCES: Marin-Padilla, M.: Abnormal Neuronal Differentiation (Functional Maturation) in Mental Retardation. In: Bergman, D. (ed.). Morphogenesis and Malformations of Face and Brain. Ori. Art. Ser. Vol. XI, #7. The National Foundation - March of Dimes. Alam Liss, Inc., New York, 1975, pp. 133-153. Marin-Padilla, M. and Marin-Padilla, T.M.: Malformations of the occipital bone in human chondrodystrophies. Am. J. Path. 82: 4a, 1976.